Coating material, coated fertilizer, and method for producing coated fertilizer

Abstract

To provide a coating material having superior controlled-release capability for fertilizer.SOLUTION: The coating material of the present invention is used for coating fertilizer, the coating material comprising an ion-crosslinkable polymer, an ion-crosslinking agent, and an environmentally degradable resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coated material, a coated fertilizer, and a method for producing the coated fertilizer. [Background technology]

[0002] Various developments have been made so far regarding fertilizer coating technologies. For example, the technology described in Patent Document 1 is known as this type of technology. Patent Document 1 describes coated granular urea having granular urea and a talc coating that coats the surface of the granular urea (Claim 1, Examples, etc. of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-007167 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that there is room for improvement in the controlled release of fertilizer in the coating material as described in Patent Document 1 above. [Means for solving the problem]

[0005] As a result of further investigation, the present inventors have found that by using a coating material that is a composite of an ionically crosslinkable polymer and an ionically crosslinking agent and an environmentally degradable resin, it is possible to appropriately control the sustained release of the fertilizer to be coated, and have thus completed the present invention.

[0006] According to one aspect of the present invention, there are provided the following coated material, coated fertilizer, and method for producing the coated fertilizer. 1. A coating material used to coat fertilizer, A coating material comprising an ionically crosslinkable polymer, an ionically crosslinking agent, and an environmentally degradable resin. 2. The coating material according to 1., The ionic crosslinking agent comprises one or more selected from the group consisting of the following components (B), (C), and (D) when the ionically crosslinkable polymer contains the following component (A), and the ionic crosslinking agent comprises one or more selected from the group consisting of the following components (A), (C), and (D) when the ionically crosslinkable polymer contains the following component (B) polycation. (A) a polyanion having a monovalent or divalent or higher anionic group, or a salt containing the polyanion (B) A polycation having a monovalent or divalent or higher cationic group, or a salt containing the polycation (C) Inorganic cations having monovalent or divalent or higher cations, or salts containing such inorganic cations (D) An anionic monomer having a monovalent or divalent or higher anionic group, or an acid containing such an anionic monomer 3. The coating material according to 1. or 2., A coating material, wherein the shape of at least one of the ionically crosslinkable polymer and the ionically crosslinking agent, as determined by SEM image observation, is one or more selected from the group consisting of granular, flat, fibrous, polyhedral, crushed, and irregular shapes. 4. The coating material according to any one of 1. to 3., The coating material, wherein the period during which the dissolution rate of the coating material at 25°C reaches 80 mass % is 2 days or more and 180 days or less. 5. The coating material according to any one of 1. to 4., Contains inorganic fillers, The coating material, wherein the inorganic filler comprises one or more selected from the group consisting of silica, talc, magnesium oxide, calcium oxide, alumina, titanium oxide, calcium carbonate, clay, potassium titanate, mica, glass flakes, whiskers, ferrite, iron oxide, zeolite, and magnesium sulfate. 6. The coating material according to 5., A coating material in which the content of the inorganic filler is 50% by mass or less relative to 100% by mass of the coating material. 7. Fertilizer and a coating layer that coats at least a portion of the surface of the fertilizer; A coated fertilizer, wherein the coating layer comprises the coating material according to any one of 1. to 6. 8. A method for producing a coated fertilizer, comprising the step of forming a coating layer on at least a part of the surface of the fertilizer using the coating material according to any one of 1. to 6. [Effects of the Invention]

[0007] According to the present invention, there are provided a coated material, a coated fertilizer, and a method for producing a coated fertilizer, which are excellent in controlled sustained release of a fertilizer. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an apparatus for evaluating sustained urea release. DETAILED DESCRIPTION OF THE INVENTION

[0009] An outline of the coating material of this embodiment will be described.

[0010] The coating material of this embodiment contains an ionically crosslinkable polymer, an ionically crosslinking agent, and an environmentally degradable resin, and is a material used to coat fertilizer.

[0011] Moreover, the coated fertilizer of the present embodiment comprises a fertilizer and a coating layer that coats at least a part of the surface of the fertilizer, and the coating layer contains the above-mentioned coating material.

[0012] According to the findings of the present inventors, it has been found that by combining different materials, namely, an ionically crosslinkable polymer and an ionically crosslinking agent with an environmentally degradable resin, it is possible to appropriately control the sustained release of fertilizer components (specifically, urea, etc.) in the coating material. Although the detailed mechanism is unclear, it is speculated that ionically cross-linkable polymers and ionically cross-linking agents have a high affinity for water, while environmentally degradable resins have a low affinity for water, and therefore, by combining different materials with different degrees of water affinity, it is possible to appropriately adjust the water affinity of the coating material and control the sustained release of fertilizer components such as urea.

[0013] We will explain the urea sustained-release mechanism in typical coated fertilizers. First, when water vapor passes through the coating layer that covers the fertilizer, the urea contained in the fertilizer, which is deliquescent, absorbs moisture and becomes aqueous, resulting in a highly concentrated urea solution. This causes internal expansion and osmotic pressure, which causes cracks in the coating layer. The urea inside is then released to the outside through the membrane cracks in the coating layer. In short, the typical urea sustained-release route is one that passes through membrane cracks formed inside the coating layer as the urea becomes aqueous.

[0014] In contrast, the sustained release pathways for urea and the like in this embodiment are presumed to be the following two. The first sustained release pathway is via water swelling that occurs inside the coating layer. When water vapor penetrates into the interior of the coating layer, moisture absorption and / or water absorption by the ionically cross-linkable polymer and ionically cross-linking agent promotes penetration of the external water into the interior of the coating layer, causing water swelling there. The second sustained release pathway is through the membrane cracks inside the coating layer formed by the above-mentioned water swelling. When the coated fertilizer comes into contact with external water, the penetration of water into the coating layer is initially promoted by the ion-crosslinking polymer and ion-crosslinking agent. However, as the water penetration progresses further, the above-mentioned water swelling causes internal volume expansion and an increase in internal pressure, resulting in the formation of membrane cracks inside the coating layer. It can be assumed that urea dissolved in water inside the coating layer is gradually released to the outside of the coating layer through these two routes. The first and second sustained-release pathways are different from the general urea sustained-release pathways described above, but they can be formed by appropriately controlling the water affinity of the coating material through the combined use of an ionically crosslinkable polymer and an ionically crosslinking agent with an environmentally degradable resin.

[0015] <Coating material> Each component of the coating material of this embodiment will be described in detail below.

[0016] The coating material is a resin composition containing an ionically crosslinkable polymer, an ionically crosslinking agent, and an environmentally degradable resin.

[0017] The environmentally degradable resin can be any resin that is decomposed by the action of natural microorganisms such as bacteria, and partially or entirely becomes water, carbon dioxide, etc., and circulates back into nature, and is preferably a material that complies with the biodegradability test in accordance with ISO 14855-2 (JIS K 6953-2).Known environmentally degradable resins can be used.

[0018] The environmentally degradable resin includes an environmentally degradable resin A having a main chain but no side chains. The environmentally degradable resin A may contain one or more of the specific examples of environmentally degradable resins described below. Furthermore, the environmentally degradable resin may contain, in addition to the environmentally degradable resin A, an environmentally degradable resin B having a main chain and a side chain. In this specification, the main chain includes a structure in which one or more repeating units contained in the molecule of the environmentally degradable resin are bonded, and a hydroxyl group, a carboxyl group, an amino group, or the like may be bonded to each of both ends of the main chain. On the other hand, the side chain includes a structure branched from a part of the main chain other than both ends. The side chain has one or more specific functional groups in at least one repeating unit in the main chain. The functional group is bonded to the carbon skeleton (carbon chain) that constitutes the side chain, and in the case of a functional group containing carbon atoms, the carbon atoms in the functional group may constitute at least a part or all of the carbon skeleton. Specific examples of functional groups include hydrophobic groups and hydrophilic groups, but preferably include at least a hydrophobic group. Hydrophobic groups may include hydrocarbon groups such as aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Hydrophilic groups may include carboxylic acid groups, sulfonic acid groups, hydroxyl groups, and amino groups (however, groups consisting of "=O" directly bonded to carbon atoms in the main chain do not need to be included in the above-mentioned hydrophilic groups). An example of the environmentally degradable resin A may include an environmentally degradable resin having a main chain containing an ester structure but no side chain, and may be selected from, for example, aliphatic polyester resins other than polylactic acid, aromatic aliphatic polyester resins, etc. On the other hand, an example of the environmentally degradable resin B may include an environmentally degradable resin having a main chain and side chain containing an ester structure, and may be selected from, for example, polylactic acid, PHA resins, P3HB resins, etc. The environmentally degradable resin may contain other environmentally degradable resins than the environmentally degradable resin A and the environmentally degradable resin B, as long as the effect of the invention is not impaired.

[0019] Specific examples of environmentally degradable resins include biodegradable plastics, such as polyester resins such as aliphatic polyester resins, aromatic aliphatic polyester resins, and polyhydroxyalkanol (PHA) resins, and non-polyester resins such as natural polymers. These may be used alone or in combination of two or more. The aliphatic polyester resin, aromatic aliphatic polyester resin, and PHA resin may each be partially or entirely derived from biomass or petroleum-derived raw materials. The environmentally degradable resin may contain either a biomass-derived resin or a natural polymer alone, or may contain two or more of these, for example, a biomass-derived resin and a petroleum-derived resin. The aliphatic polyester resin may contain one or more of, for example, polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxybutyrate, polycaprolactone (PCL), polybutylene succinate / adipate (PBSA), polymalic acid, polyglycolic acid (PGA), polydioxanone, poly(2-oxetanone), etc. The aliphatic polyester resin may contain any of these alone or may contain a copolymer containing two or more of these. The aromatic aliphatic polyester resin is a polyester resin having both an aromatic moiety and an aliphatic moiety, and may include, for example, one or more of polybutylene succinate / terephthalate (PBST), polybutylene adipate / terephthalate (PBAT), polytetramethylene adipate / terephthalate, polyethylene adipate terephthalate (PEAT), and the like. The PHA-based resin may include, for example, a P3HB-based resin containing polyhydroxyalkanoate and / or 3-hydroxybutyrate units. The P3HB-based resin may be a polymer containing only 3-hydroxybutyrate units, or may be a copolymer containing repeating units other than 3-hydroxybutyrate units. Specific examples of P3HB-based resins include poly3-hydroxybutyrate (PHB), poly(3-hydroxybutyrate / 3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB3HV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate). The poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) (PHB4HB), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (PHB3HO), poly(3-hydroxybutyrate-co-3-hydroxyoctadecanoate) (PHB3HOD), poly(3-hydroxybutyrate-co-3-hydroxydecanoate) (PHB3HD), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (PHB3HV3HH), and the like may be contained in one or more thereof. The natural polymer may include, for example, one or more of starch, cellulose, cellulose acetate, cellulose ester resin, starch, esterified starch, chitin, chitosan, gluten, gelatin, zein, soy protein, collagen, keratin, and the like. Without being limited thereto, the environmentally degradable resin may include, in addition to the above-mentioned polyester-based resins, polyamides having an ester structure in the main chain as environmentally degradable resins having a main chain containing an ester structure, and in addition to the above-mentioned natural polymers, non-polyester-based resins may include polyvinyl alcohol (PVA), polyamide 4 (PA4), biodegradable polycarbonates (PC) such as aliphatic polycarbonates, and the like.

[0020] Here, the environmentally degradable resin may contain the same type of aliphatic polyester resin, aromatic-aliphatic polyester resin, and PHA resin, or two or more different types. When containing different types, the environmentally degradable resin may include a combination of an aliphatic polyester resin and an aromatic-aliphatic polyester resin, a combination of an aliphatic polyester resin and a PHA resin, a combination of an aromatic-aliphatic polyester resin and a PHA resin, or a combination of an aliphatic polyester resin, an aromatic-aliphatic polyester resin, and a PHA resin. In this case, the PHA resin may include at least a P3HB resin, or may include only a P3HB resin. The environmentally degradable resin may contain the above-mentioned polyester resin alone, or may contain a polyester resin and a non-polyester resin, or a copolymer of a polyester resin and a non-polyester resin.

[0021] The lower limit of the content of the environmentally degradable resin in the coating material is, for example, 10% by mass or more, preferably 12.5% ​​by mass or more, and more preferably 15% by mass or more, based on 100% by mass of the total content of the ionically crosslinkable polymer, the ionically crosslinking agent, and the environmentally degradable resin. On the other hand, the upper limit of the content of the environmentally degradable resin contained in the coating material is not particularly limited, but may be 99.9% by mass or less, 99.7% by mass or less, or 99.5% by mass or less, based on 100% by mass of the total content of the ionically crosslinkable polymer, ionically crosslinking agent, and environmentally degradable resin. The content of the environmentally degradable resin A is, for example, 50 to 99 mass %, preferably 55 to 97.5 mass %, and more preferably 60 to 95 mass %, relative to 100 mass % of the environmentally degradable resin.

[0022] An ionically crosslinkable polymer is a polymer that has ionically crosslinking groups. The ionic crosslinking agent is an agent that itself serves as a crosslinking point for an ionic crosslinking reaction. The ionically crosslinkable polymer and the ionically crosslinking agent may each be contained in one kind or in two or more kinds.

[0023] The ionically crosslinkable polymer is in the form of a solid or liquid at room temperature and under normal pressure. The ionic crosslinking agent is in the form of a solid or liquid at room temperature and under normal pressure. The forms of the ionically crosslinkable polymer and the ionically crosslinking agent can be used in any combination, but a solid ionically crosslinkable polymer and a solid ionically crosslinking agent may be used, or a solid ionically crosslinkable polymer and a liquid ionically crosslinking agent may be used.

[0024] The shape of at least one of the solid ionically cross-linkable polymer and the solid ionically cross-linking agent may include, for example, one or more selected from the group consisting of granular, flat, fibrous, polyhedral, and irregular shapes. By using such granular shapes, dispersibility in the environmentally degradable resin can be improved. In this embodiment, the shapes of the ionically cross-linkable polymer and the ionically cross-linking agent can be measured by observing SEM images.

[0025] The ionically crosslinkable polymer preferably contains at least one of the following components (A) and (B). On the other hand, the ionic crosslinker is When the ionically crosslinkable polymer contains the following component (A), it is preferable that it contains one or more selected from the group consisting of the following components (B), (C), and (D): When the ionically crosslinkable polymer contains the following component (B), it preferably contains one or more selected from the group consisting of the following components (A), (C), and (D). (A) a polyanion having a monovalent or divalent or higher anionic group, or a salt containing the polyanion (B) A polycation having a monovalent or divalent or higher cationic group, or a salt containing the polycation (C) Inorganic cations having monovalent or divalent or higher cations, or salts containing one or more of the inorganic cations (D) An anionic monomer having a monovalent or divalent or higher anionic group, or an acid containing such an anionic monomer

[0026] In this specification, the valence in (A), (B), and (D) refers to the valence per ionic functional group (ionically dissociating group) contained in the monomer or polymer. Taking the example of an ionic functional group in the side chain of a polymer (macromolecule), carboxylic acid is monovalent, and dicarboxylic acid (oxalic acid, fumaric acid, etc.) is divalent. Meanwhile, in the case of (C), sodium ions are monovalent, and calcium ions are divalent. To give a specific example, polyacrylic acid polymers are classified as "polyanions having monovalent anionic groups," and alkylphosphonic acid polymers are classified as "polyanions having divalent anionic groups." In addition, in polyacrylic acid or a polymer containing acrylic acid as a component, when acrylic acid forms a calcium salt, it is classified as a "salt containing a polyanion" in which the monovalent anion group forms a salt with a divalent cation. Furthermore, in a polymer containing phosphonic acid as a constituent element, when the phosphonic acid forms a sodium salt, the polymer is classified as a "salt containing a polyanion" in which the divalent anion group forms a salt with a monovalent cation. Basically, a polymer whose main chain has a repeating structural unit α with an anionic group is called a "polyanion" (polymeric anion). On the other hand, a polymer whose main chain has a repeating structural unit β with a cationic group is called a "polycation" (polymeric cation). However, when the main chain of a polymer contains repeating structural units α and β, a polymer whose molecule contains the same or more repeating structural units α than the number of repeating structural units β is called a "polyanion," and conversely, a polymer whose molecule contains more repeating structural units β than the number of repeating structural units α is called a "polycation." A monomer that has an anionic group but does not have a repeating structural unit α having an anionic group is referred to as an "anionic monomer."

[0027] (A) "Polyanion having monovalent or divalent or higher anionic groups" preferably includes one or more polyanions A1 selected from the group consisting of polysaccharides containing at least one of carboxylic acid, sulfonic acid, and phosphoric acid in the molecule, and complex carbohydrates containing polysaccharides. The polyanion A1 preferably includes at least one of carboxylic acid and sulfonic acid.

[0028] As used herein, a monosaccharide is a sugar composed of one type of sugar. Examples of sugars include glucose, mannose, galactose, glucosamine, galactosamine, xylose, sialic acid, glucuronic acid, iduronic acid, fucose, maltose, trehalose, and lactose. In this specification, a polysaccharide is a saccharide formed by glycosidic bonds between two or more monosaccharides. A polysaccharide may be a homopolysaccharide, which has only one type of monosaccharide, or a heteropolysaccharide (sometimes called a complex polysaccharide), which has two or more types of monosaccharides. Furthermore, the polysaccharide may be any polysaccharide as long as it has a sugar chain (main chain) consisting of a repeating structure of structural units derived from monosaccharides, and functional groups may or may not be formed on the side chains of the sugar chain. Examples of functional groups formed on the side chains include polar functional groups such as a carboxyl group, a sulfonic acid group, an amide group, an acetyl group, an acetylamide group, and an amino group. As used herein, a glycoconjugate is a complex in which a polysaccharide is covalently bonded to other biological compounds other than sugars, such as proteins, lipids, peptides, etc. Examples of glycoconjugates include biopolymers such as glycoproteins, proteoglycans, and glycolipids.

[0029] The polysaccharide in the polyanion A1 may include, for example, one or more selected from the group consisting of alginic acid, carboxymethylcellulose, carrageenan, homogalacturonan, and glycosaminoglycan. Furthermore, the complex carbohydrate in the polyanion A1 may contain, for example, one or more selected from the group consisting of hyaluronic acid and chondroitin sulfate.

[0030] In another embodiment, (A) "a polyanion having a monovalent or divalent or higher anionic group" may include one or more polyanions A2 selected from the group consisting of lignosulfonic acid and polyglutamic acid. That is, (A) may include polyanion A1 alone, polyanion A2 alone, or both polyanion A1 and polyanion A2. Furthermore, the salt containing (A) a "polyanion having a monovalent or divalent or higher anionic group" may include a salt of the polyanion with a monovalent cation, i.e., an anionic compound in which an anionic group of the polyanion forms a salt with a monovalent cation, or may include a salt of a polyanion having at least one of polyanion A1 and polyanion A2 with a monovalent cation. (A) The salt containing the polyanion may include, as the monovalent cation, one or more ions selected from the group consisting of sodium ions, potassium ions, ammonium ions, and phosphonium ions.

[0031] (B) "Polycations having monovalent or divalent or higher cationic groups" include, for example, polylysine and chitosan. Furthermore, the salt containing (B) a "polycation having a monovalent or divalent or higher cationic group" may include a salt of the polycation with a monovalent anion, i.e., a cationic compound formed by the cationic group of the polycation and a monovalent anion. The salt containing (B) the polycation may include, as the monovalent anion, one or more ions selected from the group consisting of chloride ions, hydroxide ions, fluoride ions, bromide ions, iodide ions, acetate ions, and nitrate ions.

[0032] The inorganic cation having a monovalent cation may include, for example, one or more selected from the group consisting of sodium ions, potassium ions, and ammonium ions. (C) The inorganic cation having a valence of two or more may include, for example, one or more ions selected from the group consisting of calcium ions, magnesium ions, and aluminum ions. The salt containing one or more of (C) "inorganic cations having a monovalent or divalent or higher cation" may include a salt of one or more of the inorganic cations with a monovalent or divalent or higher inorganic anion, and specifically may include an ionic compound containing (C) an inorganic cation having a monovalent cation and / or (C) a divalent or higher inorganic anion and one or more inorganic anions selected from the group consisting of sulfate ions, chloride ions, hydroxide ions, phosphate ions, carbonate ions, fluoride ions, bromide ions, iodide ions, nitrate ions, and acetate ions.

[0033] (D) The anionic monomer having a monovalent, divalent or higher anionic group may include an anionic monomer having one or more carboxyl groups, or may include an anionic monomer having a carboxylate group. (D) The acid containing an anionic monomer having a monovalent, divalent or higher anionic group may contain an acid in which a proton is bonded to the anionic group of the anionic monomer. (D) Examples of the acid containing the anionic monomer include anionic monomers having one or more carboxyl groups, such as oxalic acid, fumaric acid, ethylenediaminetetraacetic acid (EDTA), citric acid, adipic acid, etc. These may be used alone or in combination of two or more.

[0034] The weight average molecular weight of at least one of component (A) and component (B) may be, for example, 1,000 or more and 10,000,000 or less. The molecular weight of the raw material monomer of component (A), the raw material monomer of component (B), and / or the anionic monomer or acid containing the anionic monomer of component (D) may be, for example, 1 to less than 1,000. In this specification, the weight average molecular weight is a value calculated in terms of polystyrene.

[0035] The coating material may also contain one or more selected from the group consisting of (X) hydrates of the ionic crosslinkers described above, (Y) inorganic hydrates other than (X), and (Z) sodium silicate. Specific examples of (Y) inorganic hydrates that can be used include sodium carbonate decahydrate, sodium acetate trihydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dihydrate, disodium hydrogen phosphate heptahydrate, disodium hydrogen phosphate octahydrate, disodium hydrogen phosphate dodecahydrate, sodium dihydrogen phosphate monohydrate, sodium dihydrogen phosphate dihydrate, magnesium chloride hexahydrate, cobalt chloride hexahydrate, copper(II) sulfate pentahydrate, cobalt(II) iodide hexahydrate, tin(II) chloride dihydrate, and iron(III) oxide hydrate.

[0036] The coating material may contain an ionically cross-linked material having at least ionic cross-links in its molecules, or may not contain an ionically cross-linked material.

[0037] The ionically cross-linked material preferably comprises an ionically cross-linked water-absorbing polymer. Compared to polyolefin resins, ionically cross-linked water-absorbing polymers can absorb water and swell. Even when an ionically cross-linked water-absorbing polymer that has absorbed water gels, it is believed that the fertilizer inside dissolves in the water in the gel and is released to the outside. Note that the ionically cross-linked water-absorbing polymer only needs to be able to absorb water, and it does not matter whether it can absorb oil other than water or not. The weight average molecular weight of the ionically cross-linked material and the ionically cross-linked water-absorbent polymer may each be, for example, 1,000 or more and 10,000,000 or less.

[0038] The ionically crosslinked water-absorbing polymer preferably contains at least one of the following (i) to (vi) as a polymer salt containing at least two of the following (A') to (D'). (i) (A') and (C'), (ii) (A'), (C') and (D') (iii) (A'), (B'), and (C') (iv) (A') and (B') (v) (B') and (D') (vi) (A'), (B'), (C') and (D') (A') Polyanion having monovalent or divalent or higher anionic groups (B') Polycation having monovalent or divalent or higher cationic groups (C') Polyvalent inorganic cations having monovalent or divalent or higher cations (D') Anionic monomer having a monovalent or divalent or higher anionic group

[0039] The coating material can improve its seawater decomposition ability by containing the above polymer salt as the ionically cross-linked water-absorbing polymer. The term "seawater decomposability" refers to a change in the properties of the polymer salt that makes it more soluble in aqueous solvents due to an ion exchange reaction between ions present in seawater and ions in the polymer salt. When the coating material dissolves and fragments in seawater, the surface area increases, increasing the number of microorganisms that come into contact with the surface, which is expected to accelerate the decomposition of the environmentally degradable resin.

[0040] The mechanism of seawater decomposition will be explained using an example in which the ionically cross-linked water-absorbent polymer contains the polymer salts (A') and (C') as the combination (i) above. However, the ionically cross-linked water-absorbent polymer is not limited to this. Ionically cross-linked polymers of alginate polymers (polyanions with monovalent anionic groups) and calcium ions (polyvalent inorganic cations) form ionic cross-linked structures in water, but in salt water (seawater), the calcium ions are exchanged for sodium, dissociating the cross-links, making the polymer soluble in salt water.

[0041] In another embodiment, the ionically crosslinked water-absorbing polymer is preferably a polymer salt containing at least one of (A') a polyanion having a monovalent or divalent or higher anionic group and (D') an anionic monomer having a monovalent or divalent or higher anion. More specifically, it is more preferable to use a polymer salt containing at least one of the above (i) and (ii).

[0042] The coating material may or may not contain, as the ionically crosslinked water-absorbent polymer, an ionically crosslinked material obtained by reacting the above-mentioned ionically crosslinkable polymer with the above-mentioned ionically crosslinking agent.

[0043] The coating material may contain, in addition to the ionically crosslinkable polymer, the ionically crosslinking agent, and the environmentally degradable resin, other additives such as inorganic fillers, surfactants, sizing agents, hydrophobic substances, functional additives, etc. These may be contained alone or in any combination of two or more.

[0044] The coating material may or may not contain inorganic fillers. The inorganic filler may be any inorganic filler that is poorly soluble or insoluble in water, and may include, for example, one or more selected from the group consisting of silica, talc, magnesium oxide, calcium oxide, alumina, titanium oxide, calcium carbonate, clay, potassium titanate, mica, glass flakes, whiskers, ferrite, iron oxide, zeolite, and magnesium sulfate. Among these, silica, talc, calcium carbonate, clay, mica, etc. are preferred from the viewpoints of price and availability.

[0045] The upper limit of the content of the inorganic filler is, for example, 50% by mass or less, preferably 49% by mass or less, and more preferably 48% by mass or less, based on 100% by mass of the coating material, which can improve the coating strength of the coating material. The lower limit of the content of the inorganic filler is, for example, 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more, based on 100% by mass of the coating material. This allows the moisture permeation rate to be controlled low due to the water blocking effect.

[0046] The coating material may contain at least one of a surfactant and a sizing agent, or may contain neither of them. The surfactant and the sizing agent can control the dispersion state of the ionically crosslinked material. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. Among these, anionic surfactants and nonionic surfactants are preferred. Examples of sizing agents include natural sizing agents, synthetic sizing agents, reactive sizing agents, special sizing agents, etc. Among these, natural sizing agents and synthetic sizing agents are preferred. These may be contained alone or in any combination of two or more.

[0047] The coating material may include a hydrophobic substance selected from the group consisting of waxes, oils, fatty acids, and the like. The hydrophobic substance is any one of waxes, oils and fats, and fatty acids, or a mixture of two or more of the group consisting of these, and may include, for example, one or more selected from the group consisting of hydrocarbon waxes, fatty acid waxes, higher alcohol waxes, glycerin fatty acid esters, and fatty acids. The coating material may also contain a hydrophobic substance such as polyester polyol or rosin resin. The addition of polyester polyol or rosin resin can control fluidity and moisture permeability. The polyester polyol may be biodegradable. The polyester polyol may be, for example, a copolymer of at least an organic acid and a glycol. The organic acid may include an aliphatic dicarboxylic acid such as adipic acid or sebacic acid, and, if necessary, an aromatic dicarboxylic acid. The glycol may include, for example, ethylene glycol, butanediol, hexanediol, etc. Examples of rosin resins include rosin ester, hydrogenated rosin ester, modified rosin, maleated rosin, fumarated rosin, maleated rosin ester, disproportionated rosin ester, and polymerized rosin ester. Here, the wax may be any one of hydrocarbon waxes, fatty acid waxes, and higher alcohol waxes, or a mixture thereof. The fatty acid wax may contain, for example, one or more waxes selected from the group consisting of aliphatic esters, aliphatic ketones, aliphatic amides, and fatty acid metal soaps. The wax may be any of natural wax, synthetic wax, and modified wax. Natural waxes include those derived from plants, animals, minerals, and petroleum. Examples of fats and oils include glycerin fatty acid esters. The glycerin fatty acid esters may include any one of monoglycerin fatty acid esters, diglycerin fatty acid esters, and triglycerin fatty acid esters, or a mixture of two or more of these. The glycerin fatty acid esters may also include polyglycerin fatty acid esters, such as those in which one hydroxyl group of glycerin is dimerized via an ether bond. Examples of fatty acids include fatty acids having less than 10 carbon atoms and higher fatty acids having 10 or more carbon atoms. Fatty acids may include straight-chain fatty acids having a main chain and no side chains, branched fatty acids having a main chain and a side chain, and / or cyclic fatty acids having at least one ring structure. Fatty acids may also include fatty acid derivatives such as hydroxy fatty acids having at least one hydroxyl group and polymers of hydroxy fatty acids. These may be used alone or in combination of two or more. The fatty acids and aliphatic skeletons each contain saturated bonds and / or unsaturated bonds. The glycerin fatty acid esters may include highly purified products that have been purified by distillation or the like.

[0048] The hydrophobic substance may include one or more of the following waxes and vegetable oils. Specific examples of waxes include natural waxes such as carnauba wax, beeswax, and rice wax; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as Fischer-Tropsch wax and polyethylene wax. Specific examples of vegetable oils include palm oil, soybean oil, rapeseed oil, sunflower oil, palm kernel oil, cottonseed oil, peanut oil, olive oil, coconut oil, corn oil, sesame oil, linseed oil, safflower oil, rice oil, and perilla oil.

[0049] The period required for the elution rate of the coating material to reach 80 mass % at 25° C. is, for example, 2 to 180 days, preferably 3 to 170 days, and more preferably 4 to 160 days. By using the above index, it becomes possible to appropriately control the urea sustained release properties of the coating material.

[0050] The urea elution rate of the coating material or the raw material components used in the coating material can be measured by the following procedure.

[0051] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an apparatus for evaluating the sustained release of urea. (Preparation of 50 evaluation samples) First, the coating material is formed into a film having a thickness of about 100 μm, and the resulting film is punched into a circle having a diameter of 15 mm to obtain the film-like test piece 10. Next, using a tablet molding machine, solid urea (specific gravity: approximately 1.3) is tableted into a cylindrical tablet having a height of 1 mm, a diameter of 10 mm, and a volume of approximately 78 mm3, to obtain a cylindrical urea tablet 20 having flat upper and lower surfaces 21. Next, the processed film-like test piece 10 is placed so that the inner surfaces 13 face the upper and lower surfaces of the urea tablet 20, and these side surfaces 23 are fixed using ring-shaped silicone rubber (waterproof member 30) to produce an evaluation sample 50.

[0052] (Measurement of urea release amount) Prepare standard solutions of known concentrations of urea in the range of 1 mg / mL to 12 mg / mL, and prepare a calibration curve showing the relationship between absorbance and urea concentration. The evaluation sample 50 is subjected to a water treatment by immersing it in distilled water (water 60) stored in a polypropylene container 70 at room temperature of 25°C and atmospheric pressure, as shown in Fig. 1. During the water treatment, the outer surface 11 of the film-like test piece 10 is kept in contact with the water 60. Immediately after the water treatment, the absorbance of the water 60 at a wavelength of 450 nm is measured over time using an absorbance meter, and the urea concentration is determined from a calibration curve. From the obtained results, it is possible to measure the amount of urea in the urea tablet 20 that has migrated into the external water 60 (urea dissolution rate). From the urea dissolution rate, it is possible to calculate the period (days) until the urea dissolution rate reaches 10% by mass and the period (days) until the urea dissolution rate reaches 80% by mass. It is also possible to measure the urea concentration under conditions in which the temperature during the water treatment is changed from room temperature to, for example, 35°C, and measure the dissolution rate at 35°C.

[0053] The coating material may be in the form of a solid, a liquid (which may or may not contain an organic solvent), or a viscous material.

[0054] Examples of the shape of the solid coating material include powder, granules, pellets, briquettes (lumps, bricks), crushed (flakes), strands (filaments), rods, and sheets. As a molding method, a known method can be used depending on the shape. Powders or granules can be produced by pulverizing or cutting the melt-kneaded product, and if necessary, treatment such as classification may be carried out. The pellets can be produced by, for example, cutting a strand obtained by extruding the molten mixture through a die. Briquettes can be produced by compressing and molding the powder or granules, or by molding the melt-kneaded mixture in a mold. The melt-kneaded material can be formed into a film or sheet by calendering, T-die extrusion, cast molding, lamination molding or the like. The flakes can be produced by forming the melt-kneaded material into a film or sheet shape, and then breaking or cutting the film or sheet.

[0055] The viscous coating material may be one in which at least one of the components has absorbed moisture, causing the forming material to gel, or one in which the forming material has softened due to the inclusion of a liquid component.

[0056] The coating material of this embodiment is It may be provided as a one-part resin composition, It may also be provided as a multiple composition of two or more components.

[0057] (1) The one-component resin composition can contain the following four types of components, broadly classified. Ion-crosslinkable polymer Ionic Crosslinkers environmentally degradable resin Other additives (inorganic fillers, surfactants, sizing agents, hydrophobic substances, functional additives, etc.)

[0058] Hereinafter, each component may be referred to by its abbreviation. Ionically crosslinkable polymer: Component O Ionic crosslinker: Component P Environmentally degradable resin: Component Q Other additives: Component R Here, {} represents a set. Component O includes the exemplary collection of ionically crosslinkable polymers previously described. Component P includes the exemplary collection of ionic crosslinkers described above. Component Q includes the exemplary collection of environmentally degradable resins described above. Component R (other additives) further includes the following set: R1: inorganic filler R2: Surfactant R3: Sizing agent R4: Hydrophobic substance R5: Functional additives Therefore, if we subdivide the "components {O, P, Q, R}", O, P, Q R1, R2, R3, R4, R5 There are a total of eight "component types" (O / P / Q / R1 / R2 / R3 / R4 / R5).

[0059] In this embodiment, the two or more compositions can be composed of two to five compositions, each of which is defined as follows. For multiple compositions of two or more drugs, the basic requirement is that the "union of each composition contains {O, P, Q, R}." (2) Two-drug composition First composition: Contains at least one of the components {O, P, Q, R}. Second composition: Contains at least one of the components {O, P, Q, R}. As long as the union of the components contained in the two compositions satisfies {O, P, Q, R}, some of the components may be in common or all of the components may be different. (3) Three-drug composition First composition: Contains at least one of the components {O, P, Q, R}. Second composition: Contains at least one of the components {O, P, Q, R}. Third composition: Contains at least one of the components {O, P, Q, R}. As long as the union of the components contained in the three compositions satisfies {O, P, Q, R}, some of the components may be in common or all of the components may be different. (4) Four-drug composition First to fourth compositions: Each contains at least one of the components {O, P, Q, R}. As long as the union of the components contained in the four compositions satisfies {O, P, Q, R}, some of them may be in common or all of them may be different. (5) Five-drug composition First to fifth compositions: Each contains at least one of the components {O, P, Q, R}. As long as the union of the components contained in the five compositions satisfies {O, P, Q, R}, some of them may be in common or all of them may be different.

[0060] In any of the two-part to five-part compositions, different component types may be combined, or different compounds within the same component type may be combined. If the component types are different, or if the same component type is different compounds, they are considered to be "different compositions." Example 1: Composition containing only O and composition containing P / Q / R Example 2: Composition containing O / P / Q / R1 and composition containing O / P / Q / R2 Example 3: Compositions Comprising O1 / P / Q / R and O2 / P / Q / R (where O1 and O2 are distinct compounds within an exemplary set of ionically crosslinkable polymers, belonging to the same component species but differing in composition) Furthermore, it is not necessary for each of the second to fifth compositions to contain component O; it is also acceptable for the first composition to contain component O while the other compositions do not. In addition, in any of the two-part to five-part compositions, the number of compound species may be the same as or greater than the number of component species. Example 1: In the case of a composition containing O / P / Q / R1, there are four compound types and four component types. Example 2: In the case of a composition containing O / P / R1 / R2, there are four compound types and four component types. Example 3: In the case of a composition containing O1 / O2 / P, there are three compound types and two component types. Furthermore, any one of the compositions from the second to fifth agents may contain at least one of a composition containing P, a composition containing Q, and a composition containing R. Furthermore, any of the compositions from the second to fifth agents may contain at least one composition that is specialized for R1 to R5 among R. When R4 is contained in multiple compositions, up to two compositions may contain R4 if there are three components, up to three compositions if there are four components, and up to four compositions if there are five components. However, the R4 contained in each composition may not be the same or may be a different compound. Furthermore, a composition containing R4 may also contain one or more components other than R4 from {O, P, Q, R}, or may contain one or more components from {P, Q, R1}. Each of the compositions of the first to fifth agents may contain components other than {O, P, Q, R}.

[0061] Regarding the combination of forms, the second agent comprises a first composition in any of {solid, liquid, viscous} form and a second composition in any of {solid, liquid, viscous} form; the third agent comprises a first composition in any of {solid, liquid, viscous} form, a second composition in any of {solid, liquid, viscous} form, and a third composition in any of {solid, liquid, viscous} form; and the fourth agent comprises a first composition in any of {solid, liquid, viscous} form and a second composition in any of {solid, liquid, viscous} form. The fifth agent comprises a first composition in any of the forms {solid, liquid, viscous}, a second composition in any of the forms {solid, liquid, viscous}, a third composition in any of the forms {solid, liquid, viscous}, and a fourth composition in any of the forms {solid, liquid, viscous}, and a fifth agent comprises a first composition in any of the forms {solid, liquid, viscous}, a second composition in any of the forms {solid, liquid, viscous}, a third composition in any of the forms {solid, liquid, viscous}, a fourth composition in any of the forms {solid, liquid, viscous}, and a fifth composition in any of the forms {solid, liquid, viscous}. In a two-drug combination, two of the components may be in the same form, in a three-drug combination, three of the components may be in the same form, in a four-drug combination, four of the components may be in the same form, or five of the components may be in the same form.

[0062] The coating material of this embodiment may be provided as a coating material set, or may be used in combination with other coating material sets. The combination of coating material sets may employ the above-described composition group. The coating material set may include a first composition and a second composition. The first composition and the second composition in the set may be contained in the same container, or may be contained in separate containers. Here, the container may be the same or different for storing the coating material set and for using it. The container for storage may be, for example, a paper container such as a paper bag, a resin container such as a resin bag or a metal-laminated resin bag, or a metal container such as a metal can, which makes storage and transportation easier. The container in use may be a process container such as a reaction vessel or a loading vessel for introducing, holding, and processing materials in a manufacturing process. At the time of use, the first composition and the second composition may be mixed and used as a coating material. Furthermore, the coating material set may include a third composition in addition to the first composition and the second composition, if necessary. The third composition may be contained in the same container as either the first composition or the second composition, or in a separate container. When using the coating material set, the third composition can be mixed with the other compositions. Furthermore, the coating material set may contain a fourth composition in addition to the first to third compositions, if necessary. The fourth composition may be contained in the same container as any of the first to third compositions, or may be contained in a separate container. When using the coating material set, the fourth composition can be mixed with the other compositions. Furthermore, the coating material set may contain a fifth composition in addition to the first to fourth compositions, if necessary. The fifth composition may be contained in the same container as any of the first to fifth compositions, or may be contained in a separate container. When using the coating material set, the fifth composition can be mixed with the other compositions.

[0063] An example of a specific example of the coating material set is as follows: However, the coating material set is not limited to this specific example.

[0064] First composition: environmentally degradable resin / Second composition: ionically crosslinkable polymer, ionically crosslinking agent, other additives First composition: environmentally degradable resin, ionically crosslinkable polymer / Second composition: ionically crosslinking agent, other additives First composition: environmentally degradable resin, ionic crosslinking agent / Second composition: ionic crosslinking polymer, other additives First composition: environmentally degradable resin, ionic crosslinking agent, ionic crosslinkable polymer / Second composition: other additives First composition: environmentally degradable resin, ionic crosslinker, ionic crosslinkable polymer, inorganic filler / Second composition: other additives (excluding inorganic filler) In the above examples of each combination, at least one of the first composition and the second composition may further contain at least one of the components {O, P, Q, R}, or may contain components other than the components {O, P, Q, R}.

[0065] The first composition may include at least an environmentally degradable resin, while the second composition may include at least a hydrophobic material. Furthermore, one or more selected from the group consisting of an ionically crosslinkable polymer, an ionically crosslinking agent, and an inorganic filler may be contained in either the first composition or the second composition, or in both. The second composition may also contain one or more selected from the group consisting of an antifoaming agent, a plasticizer, and a surface modifier for an inorganic filler. The first composition not containing a hydrophobic substance and the second composition containing a hydrophobic substance can be produced separately and, if necessary, stored or transported separately, thereby improving the ease of handling of both compositions. The above coating material set includes: A combination of a first composition containing an ionically crosslinkable polymer, an ionically crosslinking agent, an environmentally degradable resin, and an inorganic filler with a second composition containing a hydrophobic material; A combination of a first composition containing an ionically crosslinkable polymer, an environmentally degradable resin, and an inorganic filler with a second composition containing an ionically crosslinking agent and a hydrophobic substance; A combination of a first composition including an environmentally degradable resin and an inorganic filler with a second composition including an ionically crosslinkable polymer, an ionically crosslinking agent, and a hydrophobic material; A combination of a first composition containing an ionic crosslinking agent, an environmentally degradable resin, and an inorganic filler with a second composition containing an ionically crosslinkable polymer and a hydrophobic material; It may include a combination of a first composition containing an ionic crosslinking agent, an ionically crosslinkable polymer, an environmentally degradable resin and an inorganic filler, and a second composition containing an ionically crosslinkable polymer and a hydrophobic substance. In another embodiment, the coating material set may also include a third composition, which may include another type of hydrophobic material. In another embodiment, the coating material set may include a third composition and a fourth composition, and each of the third composition and the fourth composition may include a different type of hydrophobic material than the other compositions. In another embodiment, the coating material set may include a third composition to a fifth composition, and each of the third composition to the fifth composition may include a different type of hydrophobic substance from the other compositions.

[0066] Here, a method for producing the above-mentioned coating material will be described. An example of a method for producing a coating material may include a step of melt-kneading raw material components including the above-mentioned ionically cross-linkable polymer, the above-mentioned ionically cross-linking agent, and the above-mentioned environmentally degradable resin using a kneading device to obtain a solid coating material. The raw material components may also include one or more other additives.

[0067] The order in which the raw material components are fed to the kneading device is not particularly limited, but the ionically crosslinkable polymer, ionically crosslinking agent, or other additives may be added after the addition of the environmentally degradable resin. If necessary, at least two or more components contained in the raw material ingredients may be mixed in advance before kneading the raw material ingredients.

[0068] The temperature during melt kneading can be adjusted depending on the melting point or softening point of the environmentally degradable resin used, and may be, for example, 50 to 300°C, preferably 70 to 290°C, and more preferably 90 to 280°C.

[0069] The raw material components may contain adsorbed water or crystal water as moisture contained in each component of the raw material components.

[0070] Another example of a method for producing a coating material may include a step of obtaining a liquid coating material containing raw material components including the ionically crosslinkable polymer, the ionically crosslinking agent, and the environmentally degradable resin, and a solvent.

[0071] The solvent may include a solvent having a boiling point of 30°C to 210°C. The solvent is preferably an organic solvent (non-aqueous solvent), and examples thereof include halogen-based solvents such as chloroform, trichloroethylene, dichloroethane, etc.; aromatic solvents such as toluene; aliphatic solvents such as hexane; alicyclic solvents such as cyclohexane; ketone-based solvents such as acetone and MEK; ester-based solvents such as ethyl acetate; and alcohol-based solvents such as methanol, ethanol, isopropanol, etc. These may be contained alone or in any combination of two or more.

[0072] In the process of obtaining a liquid coating material, the order in which the components contained in the raw material ingredients are mixed with the solvent is not particularly limited. Heating may or may not be performed at any stage during mixing.

[0073] The liquid coating material may be a one-component liquid containing at least an ionic crosslinking agent, an ionic crosslinkable polymer, and a second liquid, or a two-component liquid containing a first liquid containing at least an ionic crosslinking agent and a second liquid containing at least an ionic crosslinkable polymer. In the case of a two-component liquid, the environmentally degradable resin is contained in at least one of the first and second liquids. At least one of the other additives may be contained in either the first or second liquid, if necessary.

[0074] <Coated fertilizer> An example of the coated fertilizer of this embodiment has a coating layer containing the solid content of the above-mentioned coating material, and a fertilizer whose surface is coated with the coating layer.

[0075] The coating layer may contain at least one of the following resin compositions (J1) to (J4) as the solid content of the coating material. The resin composition (J1) contains an ionically crosslinkable polymer, an ionically crosslinking agent, and an environmentally degradable resin. The resin composition (J2) contains an ionically crosslinkable polymer, an ionically crosslinking agent, an ionically crosslinking material, and an environmentally degradable resin. The resin composition (J3) contains only one of an ionically crosslinkable polymer and an ionically crosslinking agent, and also contains an ionically crosslinkable material and an environmentally degradable resin. The resin composition (J4) does not contain either an ionically crosslinkable polymer or an ionically crosslinking agent, and contains an ionically crosslinkable material and an environmentally degradable resin. In addition to the resin compositions (J1) to (J4), the resin composition may contain additives such as inorganic fillers, surfactants, sizing agents, hydrophobic substances, and functional additives. These may be contained alone or in any combination of two or more. The solid content of the coating material does not substantially contain the solvent contained in the liquid coating material.

[0076] The coating layer may cover at least a part of the surface of the granular fertilizer, or may cover the entire surface. The coating layer may have a single layer or multiple layers containing any of the resin compositions (J1) to (J4). The multi-layer coating layer may include, in addition to a layer containing at least components O, P, and Q from the components {O, P, Q, R}, other layers containing at least one or more of the components {O, P, Q, R}. Examples of other layers include a layer containing only one of the components {O, P, Q, R}, a layer containing only two of the components {O, P, Q, R}, a layer containing only three of the components {O, P, Q, R}, or a layer containing all of the components {O, P, Q, R}. Specific examples include a layer containing component O and component P, a layer containing component O and component Q, a layer containing component O and component R, a layer containing component O and component R1, a layer containing component O and component R2, a layer containing component O and component R3, a layer containing component O and component R4, and a layer containing component O and component R5. The coating layer is preferably in a dry state (not in a gel state having fluidity) from the viewpoint of storage in the package, etc. However, this is not a limitation when using the coated fertilizer.

[0077] The coating layer may contain functional additives as needed. The functional additive is not particularly limited as long as it is used in the coating material of the fertilizer, and examples thereof include fillers other than the above-mentioned inorganic fillers, lubricants, waxes, thickeners, adhesion promoters, surface modifiers, pH adjusters, crosslinking retarders (chelating agents), reinforcing materials, gas barrier agents, magnetic materials, decomposition inhibitors, etc. These may be used alone or in combination of two or more.

[0078] The form of the fertilizer is not particularly limited as long as it is solid in the atmosphere at 25°C. The fertilizer may be in the form of a powder, granules, pellets, briquettes, or any other granular fertilizer having a predetermined shape, for example. Among these, from the viewpoint of dispersibility, the fertilizer is preferably in the form of a sphere.

[0079] The granular fertilizer can be produced by using a known granulation method such as a fluidized bed granulation method, a tumbling granulation method, a coating granulation method, an adsorption granulation method, or an agglomeration granulation method, but the method for producing the granular fertilizer is not limited to these.

[0080] The fertilizer used can be any known fertilizer, for example, one or more of nitrogenous fertilizers, phosphorous fertilizers, and potassium fertilizers. As nitrogenous fertilizers, for example, ammonium salts and nitrates are used, and specific examples include ammonium sulfate, ammonium chloride, urea, lime nitrogen, sodium nitrate, and ammonium nitrate. Examples of phosphorus fertilizers include superphosphate, triple superphosphate, fused phosphate fertilizer, and calcined phosphate fertilizer. Examples of potassium fertilizers include potassium chloride and potassium sulfate. In addition to the above three fertilizers, the fertilizer may also contain other fertilizers (calcareous fertilizers, silicate fertilizers, manganese fertilizers, boron fertilizers, etc.) and one or more known inorganic compounds containing inorganic nutrients.

[0081] The fertilizer may contain other components as long as the effects of the present invention are not impaired. Other components may include, for example, carriers such as clay, kaolin, talc, bentonite, calcium carbonate, etc.; binders such as polyvinyl alcohol, sodium carboxymethyl cellulose, starches, etc.; and, if necessary, surfactants such as polyoxyethylene nonylphenyl ether, blackstrap molasses, animal oil, vegetable oil, hydrogenated oil, fatty acid, fatty acid metal salt, paraffin, wax, glycerin, etc. These may be used alone or in combination of two or more.

[0082] The manufacturing process of the coated fertilizer of this embodiment may include a step of forming a coating layer on at least a portion of the surface of the fertilizer using the above-mentioned coating material or a coating material obtained by the above-mentioned method for manufacturing a coating material.

[0083] As the coating method, known methods for coating the surface of solid particles can be used, and examples thereof include chemical methods such as a non-aqueous wet method, an aqueous wet method, a gas phase reaction method, and a mechachemical method, and physical methods such as a mechanical surface treatment method, a laser ablation method, an air suspension coating method, and a spray drying method. When coating the granules with a coating material, it is preferable to use a fluidized bed granulation method or a rolling granulation method. When applying such a production method, it is preferable to use a liquid coating material. However, when using a solid coating material, it is not limited to this, and it is also possible to use a varnish made by dissolving it in a solvent.

[0084] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0085] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0086] <Production of coating materials> Example 1 Sodium alginate (manufactured by Tokyo Chemical Industry Co., Ltd.) as an ionically crosslinkable polymer and aluminum sulfate 14-18 hydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as an ionically crosslinking agent were pulverized and mixed in a mortar to obtain a mixture. The resulting mixture was mixed with polybutylene succinate (PBS) as an environmentally degradable resin under heating to obtain a coating material. The content of the ionically crosslinkable polymer in 100% by mass of the coating material was 3% by mass, and the content of the ionically crosslinking agent was 15% by mass relative to 100% by mass of the ionically crosslinkable polymer.

[0087] Example 2 A coating material was produced in the same manner as in Example 1, except that calcium carbonate was added to the mixture as an inorganic filler. The content of the ionically crosslinkable polymer was 10% by mass, the content of the inorganic filler was 25% by mass, and the content of the ionically crosslinking agent was 10% by mass relative to 100% by mass of the ionically crosslinkable polymer.

[0088] <Evaluation of urea sustained release> (Preparation of 50 evaluation samples) First, the covering material was formed into a film having a thickness of about 100 μm, and the obtained film was punched into a circle having a diameter of 15 mm to obtain a film-like test piece 10. Next, using a tablet molding machine, solid urea (specific gravity: approximately 1.3) was compressed into cylindrical tablets with a height of 1 mm, a diameter of 10 mm, and a volume of approximately 78 mm3, to obtain cylindrical urea tablets 20 with flat upper and lower surfaces 21. Next, the processed film-like test piece 10 was placed so that the inner surface 13 faced the upper and lower surfaces of the urea tablet 20, and these side surfaces 23 were fixed using ring-shaped silicone rubber (waterproof member 30) to produce an evaluation sample 50.

[0089] (Measurement of urea release amount) Standard solutions of known urea concentrations in the range of 1 mg / mL to 12 mg / mL were prepared, and a calibration curve showing the relationship between absorbance and urea concentration was prepared. The evaluation sample 50 was subjected to a water treatment by immersing it in distilled water (water 60) stored in a polypropylene container 70 at room temperature of 25°C and atmospheric pressure, as shown in Fig. 1. During the water treatment, the outer surface 11 of the film-like test piece 10 was kept in contact with the water 60. Immediately after the water treatment, the absorbance of the water 60 at a wavelength of 450 nm was measured over time using an absorbance meter, and the urea concentration was determined from a calibration curve. From the obtained results, the amount of urea in the urea tablet 20 that has moved into the external water 60 (urea dissolution rate) can be measured. 80 (days) was calculated. Similarly, instead of the coating materials of Examples 1 and 2, a 100 μm thick film of PBS alone was used.80 was calculated.

[0090] According to the above <Evaluation of urea sustained release>, T 80 The results showed that the value of index T decreased in the order of PBS alone, the coating material of Example 1, and the coating material of Example 2. 80 The smaller the value, the higher the effect of the coating material in providing a sustained release rate. Therefore, by forming a composite of an ionically crosslinkable polymer and an ionically crosslinking agent with an environmentally degradable resin, a coating material with excellent controlled sustained release of urea can be realized.

[0091] <Thermal analysis> The DSC profiles of the mixture obtained above, sodium alginate alone, and aluminum sulfate 14-18 hydrate alone were measured using a differential scanning calorimeter in the temperature range of 40°C to 280°C. As a result, a shift in the endothermic peak and an increase in the endothermic amount were confirmed in the DSC profile of the mixture compared to the above two compounds alone.

[0092] <Dissolution test> The mixture obtained above, sodium alginate alone, and aluminum sulfate 14-18 hydrate alone were each dispersed in toluene in a sample tube, heated on a 100°C hot plate for about 15 minutes, and then the toluene was evaporated on a 120°C hot plate to obtain a powder. Distilled water was added to the obtained powder, and the state of the powder was observed. It was confirmed that insoluble matter was generated in the mixture, whereas the two compounds dissolved in water alone, and no insoluble matter was detected.

[0093] The results of the above-mentioned "thermal analysis" and "dissolution test" suggest that the water contained in the components such as the ionic crosslinking agent can cause at least a part of the ionic crosslinkable polymer and the ionic crosslinking agent to undergo a crosslinking reaction. [Explanation of symbols]

[0094] 10 Film test piece 11 Exterior 13 Inner 20 urea tablets 23 Side 30 Waterproofing materials 50 evaluation samples 60 water 70 containers

Claims

1. A coating material used to coat a fertilizer, A coating material comprising an ionically crosslinkable polymer, an ionically crosslinking agent, and an environmentally degradable resin.

2. The coating material according to claim 1, The ionically crosslinkable polymer contains at least one of the following components (A) and (B): When the ionically crosslinkable polymer contains the following component (A), the ionically crosslinking agent contains one or more selected from the group consisting of the following components (B), (C), and (D), A coating material, wherein when the ionically crosslinkable polymer contains the following component (B), the ionically crosslinking agent contains one or more selected from the group consisting of the following components (A), (C), and (D): (A) A polyanion having a monovalent or divalent or higher anionic group, or a salt containing the polyanion (B) a polycation having a monovalent or divalent or higher cationic group, or a salt containing the polycation (C) Inorganic cations having monovalent or divalent or higher valent cations, or salts containing one or more of the inorganic cations (D) An anionic monomer having a monovalent or divalent or higher anionic group, or an acid containing such an anionic monomer

3. The coating material according to claim 1 or 2, A coating material, wherein the shape of at least one of the ionically crosslinkable polymer and the ionically crosslinking agent as determined by SEM image observation includes one or more shapes selected from the group consisting of granular, flat, fibrous, polyhedral, crushed, and irregular shapes.

4. The coating material according to claim 1 or 2, The coating material, wherein the period during which the elution rate of the coating material at 25°C reaches 80 mass % is 2 days or more and 180 days or less.

5. The coating material according to claim 1 or 2, Contains inorganic fillers, The coating material, wherein the inorganic filler comprises one or more selected from the group consisting of silica, talc, magnesium oxide, calcium oxide, alumina, titanium oxide, calcium carbonate, clay, potassium titanate, mica, glass flakes, whiskers, ferrite, iron oxide, zeolite, and magnesium sulfate.

6. The coating material according to claim 5, A coating material, wherein the content of the inorganic filler is 50% by mass or less relative to 100% by mass of the coating material.

7. Fertilizer and a coating layer that coats at least a portion of the surface of the fertilizer; A coated fertilizer, wherein the coating layer comprises the coating material according to claim 1 or 2.

8. A method for producing a coated fertilizer, comprising the step of forming a coating layer on at least a part of the surface of a fertilizer using the coating material according to claim 1 or 2.

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